1. Field of the invention
The present invention relates to an inner fin for a heat exchanger, and in particular, to an inner fin fixedly inserted into a heat exchange tube and a manufacturing method of the same.
2. Description of the Background Art
The inner fin inserted into the heat exchanger tube in the prior art is formed of a thin plate, which can be inserted into an insertion aperture of the tube, and has a corrugated section in a widthwise direction. For example, as shown in FIG. 12, a tube 1 having a fluid passage of a flat section accommodates an inner fin 2 formed of a thin corrugated plate, which has parallel crests and troughs having a height of h.sub.0 and extending in a lengthwise direction of the tube. FIG. 12 shows the inner fin 2 partially drawn out from the tube 1, but in a practical state, the inner fin 2 is completely inserted into the tube 1, and the crest surfaces 2a of the inner fin 2 are brazed to an inner wall of the tube 1.
Passages for cooling medium are defined by inclined surfaces 2c, which extend between the crest surfaces 2a and the trough surfaces 2b, and the inner wall of the tube. These passages extend in the lengthwise direction of the tube and are partitioned from each other by the inner fin.
According to the inner fin thus formed for the heat exchanger, the passages formed between the inner wall of the tube and the surfaces of the inner fin may be clogged with contaminant such as dust and/or residue (e.g., flux residue generated in a manufacturing step) in the cooling medium flowing in the passages. If one or some passages are clogged, a total flow of the cooling medium flowing through the tube 1 decreases, and thus a heat exchanger performance decreases correspondingly of the reduction of the volume of the heat exchange medium.